Pellicle for an EUV lithography mask and a method of manufacturing thereof

ABSTRACT

A pellicle for an EUV photo mask includes a base membrane layer, a core layer disposed over the base membrane layer and one or more metallic layers disposed over the core layer.

RELATED APPLICATION

This application claims priority of U.S. Provisional Application No.62/664,524 filed on Apr. 30, 2018, the entire contents of which areincorporated herein by reference.

TECHNICAL FIELD

The disclosure relates to a pellicle for an extreme ultra violet (EUV)lithography photo mask and methods of manufacturing the pellicle.

BACKGROUND

A pellicle is a thin transparent film stretched over a frame that isglued over one side of a photo mask to protect the photo mask fromdamage, dust and/or moisture. In EUV lithography, a pellicle having ahigh transparency in the EUV wavelength region, a high mechanicalstrength and a low thermal expansion is generally required.

BRIEF DESCRIPTION OF THE DRAWINGS

Aspects of the present disclosure are best understood from the followingdetailed description when read with the accompanying figures. It isnoted that, in accordance with the standard practice in the industry,various features are not drawn to scale. In fact, the dimensions of thevarious features may be arbitrarily increased or reduced for clarity ofdiscussion.

FIG. 1 shows a cross sectional view of one of the various stages formanufacturing a pellicle for an EUV photo mask in accordance with anembodiment of the present disclosure.

FIG. 2 shows a cross sectional view of one of the various stages formanufacturing a pellicle for an EUV photo mask in accordance with anembodiment of the present disclosure.

FIG. 3 shows a cross sectional view of one of the various stages formanufacturing a pellicle for an EUV photo mask in accordance with anembodiment of the present disclosure.

FIG. 4 shows a cross sectional view of one of the various stages formanufacturing a pellicle for an EUV photo mask in accordance with anembodiment of the present disclosure.

FIG. 5 shows a cross sectional view of one of the various stages formanufacturing a pellicle for an EUV photo mask in accordance with anembodiment of the present disclosure.

FIG. 6 shows a cross sectional view of one of the various stages formanufacturing a pellicle for an EUV photo mask in accordance with anembodiment of the present disclosure.

FIG. 7 shows a cross sectional view of one of the various stages formanufacturing a pellicle for an EUV photo mask in accordance with anembodiment of the present disclosure.

FIG. 8 shows a cross sectional view of one of the various stages formanufacturing a pellicle for an EUV photo mask in accordance with anembodiment of the present disclosure.

FIG. 9 shows a cross sectional view of one of the various stages formanufacturing a pellicle for an EUV photo mask in accordance with anembodiment of the present disclosure.

FIG. 10 shows a cross sectional view of one of the various stages formanufacturing a pellicle for an EUV photo mask in accordance with anembodiment of the present disclosure.

FIG. 11 shows a cross sectional view of one of the various stages formanufacturing a pellicle for an EUV photo mask in accordance with anembodiment of the present disclosure.

FIG. 12 shows a cross sectional view of one of the various stages formanufacturing a pellicle for an EUV photo mask in accordance withanother embodiment of the present disclosure.

FIG. 13 shows a cross sectional view of one of the various stages formanufacturing a pellicle for an EUV photo mask in accordance withanother embodiment of the present disclosure.

FIG. 14 shows a cross sectional view of one of the various stages formanufacturing a pellicle for an EUV photo mask in accordance withanother embodiment of the present disclosure.

FIG. 15 shows a cross sectional view of one of the various stages formanufacturing a pellicle for an EUV photo mask in accordance withanother embodiment of the present disclosure.

FIG. 16 shows a cross sectional view of one of the various stages formanufacturing a pellicle for an EUV photo mask in accordance withanother embodiment of the present disclosure.

FIG. 17 shows a cross sectional view of one of the various stages formanufacturing a pellicle for an EUV photo mask in accordance withanother embodiment of the present disclosure.

FIG. 18 shows a cross sectional view of one of the various stages formanufacturing a pellicle for an EUV photo mask in accordance withanother embodiment of the present disclosure.

FIG. 19 shows a cross sectional view of one of the various stages formanufacturing a pellicle for an EUV photo mask in accordance withanother embodiment of the present disclosure.

FIG. 20 shows a cross sectional view of one of the various stages formanufacturing a pellicle for an EUV photo mask in accordance withanother embodiment of the present disclosure.

FIG. 21 shows a cross sectional view of one of the various stages formanufacturing a pellicle for an EUV photo mask in accordance withanother embodiment of the present disclosure.

FIG. 22 shows a cross sectional view of one of the various stages formanufacturing a pellicle for an EUV photo mask in accordance withanother embodiment of the present disclosure.

FIG. 23 shows a cross sectional view of one of the various stages formanufacturing a pellicle for an EUV photo mask in accordance withanother embodiment of the present disclosure.

FIG. 24 shows a cross sectional view of one of the various stages formanufacturing a pellicle for an EUV photo mask in accordance withanother embodiment of the present disclosure.

FIG. 25 shows a cross sectional view of one of the various stages formanufacturing a pellicle for an EUV photo mask in accordance withanother embodiment of the present disclosure.

FIG. 26 shows a cross sectional view of one of the various stages formanufacturing a pellicle for an EUV photo mask in accordance withanother embodiment of the present disclosure.

FIG. 27 shows a cross sectional view of one of the various stages formanufacturing a pellicle for an EUV photo mask in accordance withanother embodiment of the present disclosure.

FIG. 28 shows a cross sectional view of one of the various stages formanufacturing a pellicle for an EUV photo mask in accordance withanother embodiment of the present disclosure.

FIG. 29 shows a cross sectional view of pellicles for an EUV photo maskin accordance with another embodiment of the present disclosure.

FIG. 30 shows a cross sectional view illustrating a pellicle attached toan EUV photo mask in accordance with an embodiment of the presentdisclosure.

FIG. 31 is a table showing EUV transmittance values and reflectancevalues for various stacked structures.

DETAILED DESCRIPTION

It is to be understood that the following disclosure provides manydifferent embodiments, or examples, for implementing different featuresof the invention. Specific embodiments or examples of components andarrangements are described below to simplify the present disclosure.These are, of course, merely examples and are not intended to belimiting. For example, dimensions of elements are not limited to thedisclosed range or values, but may depend upon process conditions and/ordesired properties of the device. Moreover, the formation of a firstfeature over or on a second feature in the description that follows mayinclude embodiments in which the first and second features are formed indirect contact, and may also include embodiments in which additionalfeatures may be formed interposing the first and second features, suchthat the first and second features may not be in direct contact. Variousfeatures may be arbitrarily drawn in different scales for simplicity andclarity. In the accompanying drawings, some layers/features may beomitted for simplification.

Further, spatially relative terms, such as “beneath,” “below,” “lower,”“above,” “upper” and the like, may be used herein for ease ofdescription to describe one element or feature's relationship to anotherelement(s) or feature(s) as illustrated in the figures. The spatiallyrelative terms are intended to encompass different orientations of thedevice in use or operation in addition to the orientation depicted inthe figures. The device may be otherwise oriented (rotated 90 degrees orat other orientations) and the spatially relative descriptors usedherein may likewise be interpreted accordingly. In addition, the term“made of” may mean either “comprising” or “consisting of.” Further, inthe following fabrication process, there may be one or more additionaloperations in between the described operations, and the order ofoperations may be changed. In the present disclosure, the phrase “atleast one of A, B and C” means either one of A, B, C, A+B, A+C, B+C orA+B+C, and does not mean one from A, one from B and one from C, unlessotherwise explained.

A pellicle is a thin transparent film stretched over a frame that isglued over one side of a photo mask, and protects the photo mask fromparticles, dust, damages and/or contamination. A pellicle generallyrequires a higher transparency and a lower reflectivity. In UV or DUVlithography, the pellicle film is made of a transparent resin film. InEUV lithography, however, a resin based film is not proper, and anon-organic material, such as a polysilicon, silicide or graphite, isused.

In the present disclosure, the pellicle for an EUV photo mask has astacked structure of various dielectric, semiconductor and/or metallicmaterials to enhance an EUV transmittance, to reduce an EUV reflectance,to improve mechanical strength, and/or to improve thermal properties. Inparticular, the pellicle according to the present disclosure has an EUVtransmittance higher than about 85% in some embodiments, and higher thanabout 87% in other embodiments, and has an EUV reflectance lower thanabout 0.25% in some embodiments, and lower than about 0.10% in otherembodiments.

FIGS. 1-11 show a sequential manufacturing operation for a pellicle foran EUV photo mask in accordance with an embodiment of the presentdisclosure. It is understood that additional operations can be providedbefore, during, and after processes shown by FIGS. 1-11, and some of theoperations described below can be replaced or eliminated, for additionalembodiments of the method. The order of the operations/processes may beinterchangeable.

As shown in FIG. 1, a substrate 10, for example a Si wafer, is prepared.The thickness of the substrate 10 is in a range from about 500 μm toabout 1000 μm in some embodiments.

On the substrate 10, a base membrane layer 20 is formed, as shown inFIG. 2. The base membrane layer 20 functions as an etching stop layer ina subsequent substrate etching operation. The base membrane layer 20includes one or more layers of semiconductor material, such as SiC,SiGe, SiCN, Ge, or dielectric material, such as silicon oxide, siliconnitride and silicon oxynitride, or any other suitable material. In someembodiments, SiC is epitaxially formed on the substrate 10. In otherembodiments, the base membrane layer 20 can be an amorphous orpolycrystalline SiC, SiGe or Ge layer. In certain embodiments, the basemembrane layer 20 is silicon nitride. The thickness of the base membranelayer is in a range from about 0.5 nm to about 40 nm in someembodiments, and is in a range from about 1 nm to about 20 nm in otherembodiments. The base membrane layer 20 can be formed by chemical vapordeposition (CVD), physical vapor deposition (PVD), atomic layerdeposition (ALD), molecular beam epitaxy (MBE) and any other suitablefilm formation methods.

After the base membrane layer 20 is formed, a core layer 30 is formedover the base membrane layer 20, as shown in FIG. 3. The core layer 30includes one or more layers of semiconductor material, such as Si, SiC,SiGe, metal alloys, such as silicide (WSi, NiSi, TiSi, CoSi, MoSi,etc.), or dielectric material, such as silicon nitride. Thesemiconductor material can be single crystalline, poly crystalline oramorphous. In certain embodiments, a Si layer is epitaxially formed onthe SiC base membrane layer. In other embodiments, poly silicon oramorphous silicon is used as the core layer 30. The thickness of thecore layer 30 is in a range from about 10 nm to about 50 nm in someembodiments, and is in a range from about 20 nm to about 40 nm in otherembodiments. The core layer 30 can be formed by CVD, PVD, ALD, MBE andany other suitable film formation methods. In certain embodiments, acore layer 30 is not formed. In such a case, the base membrane layer 20has a thickness in a range from about 10 nm to about 30 nm, in someembodiments.

Then, a cover layer 40 is formed over the core layer 30, as shown inFIG. 4. If the core layer 30 is not formed, the cover layer 40 is formedover the base membrane layer 20. The cover layer 40 includes one or morelayers of silicon nitride, SiC or SiCN, in some embodiments. In otherembodiments, the cover layer 40 is formed by implanting impurities inthe Si core layer. The impurities can be boron, phosphorous and/orarsenic. A dose amount of the impurities in in a range from about10¹⁷-10²⁰ ions/cm⁻² in some embodiments. The thickness of the coverlayer 40 is in a range from about 0.5 nm to about 10 nm in someembodiments, and is in a range from about 1 nm to about 5 nm in otherembodiments. The cover layer 40 can be formed by CVD, PVD, ALD, MBE andany other suitable film formation methods. In certain embodiments, acover layer 40 is not formed.

Next, as shown in FIG. 5, a protection layer 50 is formed over the coverlayer 40. If the cover layer 40 and/or the core layer 30 is/are notformed, the first protection layer 50 is formed over the core layer 30or the base membrane layer 20. The protection layer 50 includes one ormore layers of dielectric material, such as silicon oxide, siliconnitride and silicon oxynitride. In certain embodiments, silicon oxide isused. The thickness of the protection layer 50 is in a range from about100 nm to about 10 μm in some embodiments. The protection layer 50 canbe formed by CVD, PVD, ALD, MBE and any other suitable film formationmethods. The first protection layer 50 includes one or more layers ofmetal based material, for example, Al, Cu, Ta, Ti, Co, Fe, Ni, TaN orTiN and their alloy, in some embodiments. The first protection layer 50also can be metal oxide, metal nitride, for example SiN, SiO or SiON, insome embodiments. In some embodiments, multiple layers with differentmaterials are used as the first protection layer 50.

Next, as shown in FIG. 6, a hard mask layer 70 is formed over the backside of the substrate 10. The hard mask layer 70 includes one or morelayers of dielectric material, such as silicon oxide, silicon nitrideand silicon oxynitride. In certain embodiments, silicon nitride is used.The thickness of the hard mask layer 70 is in a range from about 100 nmto about 1000 nm in some embodiments, and is in a range from about 200nm to about 500 nm in other embodiments. The hard mask layer 70 can beformed by CVD, PVD, ALD, MBE and any other suitable film formationmethods.

Then, a photo resist layer 80 is formed on the hard mask layer 70, asshown in FIG. 7. The thickness of the photo resist layer 80 is in arange from about 1 μm to about 3 μm in some embodiments, One or morelithography operations are performed to pattern the photo resist layer80, and subsequently, the hard mask layer 70 is patterned by one or moreetching operations to form a first opening 90 as shown in FIG. 8. Thephoto resist layer 80 is removed by suitable resist removal operations.

Then, the substrate 10 is etched to form a second opening 95, as shownin FIG. 9. In some embodiments, wet etching using KOH, TMAH(tetramethylammonium hydroxide) or EDP (ethylenediamine pyrocatechol) isperformed to etch the Si substrate 10. The substrate 10 can also beetched by dry etching process using one or more of SF₆, CF₄ and Cl₂ gas,mixed with N₂ and/or O₂ gas. In some embodiments, the substrate belowthe first opening 90 is etched to expose the base membrane layer 20. Bythis etching operation, a frame structure of the pellicle is formed by apart of the substrate 10 and a part of the hard mask layer 70.

Then, the first protection layer 50 is removed by one or more etchingoperations, as shown in FIG. 10. In some embodiments, a wet etchingoperation is used.

Next, as shown in FIG. 11, one or more metallic layers 120 and 130 areformed over the cover layer 40. In some embodiments, a first metalliclayer 120 includes a layer of Mo, Zr, Nb, B, and Ti, Ru, or othersuitable material. In some embodiments, the second metallic layer 130includes a Ru layer. In some embodiments, a Ru layer 130 formed on a Molayer 120 is used. In other embodiments, a Ru layer 130 formed on a Zrlayer 120 is used. In certain embodiments, only a Zr layer is formed onthe cover layer 40. In certain embodiments, only a Ru layer is formed onthe cover layer 40. The thickness of the first metallic layer 120 isgreater than the thickness of the second metallic layer 130 in someembodiments. The thickness of the first metallic layer 120 and thesecond metallic layer 130 is in a range from about 0.5 nm to about 20 nmin some embodiments, and is in a range from about 1 nm to about 10 nm inother embodiments. The second metallic layer 130 is thinner than thefirst metallic layer 120 in some embodiments. The first metallic layer120 and the second metallic layer 130 can respectively be formed by CVD,PVD, ALD, electro plating, and any other suitable film formationmethods. In certain embodiments, any or all of the metallic layers arefurther formed on inside walls of the second opening 95. In someembodiments, all of the layers of the pellicle are solid and non-porouslayers. In certain embodiments, all of the layers of the pellicle areinorganic.

FIGS. 12-22 show a sequential manufacturing operation for a pellicle foran EUV photo mask in accordance with an embodiment of the presentdisclosure. It is understood that additional operations can be providedbefore, during, and after processes shown by FIGS. 12-22, and some ofthe operations described below can be replaced or eliminated, foradditional embodiments of the method. The order of theoperations/processes may be interchangeable. Materials, configurations,dimensions, structures, conditions and operations the same as or similarto those explained with respect to FIGS. 1-11 may be employed in thefollowing embodiments, and some of the explanations may be omitted.Similarly, materials, configurations, dimensions, structures, conditionsand operations the same as or similar to those explained with respect toFIGS. 12-22 may be employed in the foregoing embodiments.

As shown in FIG. 12, a substrate 10, for example a Si wafer, isprepared. The thickness of the substrate 10 is in a range from about 500μm to about 1000 μm in some embodiments.

On the substrate 10, a base membrane layer 20, as an etching stop layer,is formed, as shown in FIG. 13. The base membrane layer 20 functions asan etching stop layer in a subsequent substrate etching operation. Thebase membrane layer 20 includes one or more layers of semiconductormaterial, such as SiC, SiGe, Ge, or dielectric material, such as siliconoxide, silicon nitride and silicon oxynitride, or any other suitablematerial. In some embodiments, SiC is epitaxially formed on thesubstrate 10. In other embodiments, the base membrane layer 20 can be anamorphous or polycrystalline SiC, SiGe or Ge layer. In certainembodiments, the base membrane layer 20 is silicon nitride. Thethickness of the base membrane layer is in a range from about 0.5 nm toabout 40 nm in some embodiments, and is in a range from about 1 nm toabout 20 nm in other embodiments. The base membrane layer 20 can beformed by chemical vapor deposition (CVD), physical vapor deposition(PVD), atomic layer deposition (ALD), molecular beam epitaxy (MBE) andany other suitable film formation methods.

After the base membrane layer 20 is formed, a core layer 30 is formedover the base membrane layer 20, as shown in FIG. 14. The core layer 30includes one or more layers of semiconductor material, such as Si, SiC,SiGe, metal alloys, such as silicide (WSi, NiSi, TiSi, CoSi, MoSi,etc.), or dielectric material, such as silicon nitride. Thesemiconductor material can be single crystalline, poly crystalline oramorphous. In certain embodiments, a Si layer is epitaxially formed onthe SiC base membrane layer. In other embodiments, poly silicon oramorphous silicon is used as the core layer 30. The thickness of thecore layer 30 is in a range from about 10 nm to about 50 nm in someembodiments, and is in a range from about 20 nm to about 40 nm in otherembodiments. The core layer 30 can be formed by CVD, PVD, ALD, MBE andany other suitable film formation methods. In certain embodiments, acore layer 30 is not formed. In such a case, the base membrane layer 20has a thickness in a range from about 10 nm to about 30 nm, in someembodiments.

Then, a cover layer 40 is formed over the core layer 30, as show in FIG.15. If the core layer 30 is not formed, the cover layer 40 is formedover the base membrane layer 20. The cover layer 40 includes one or morelayers of silicon nitride and SiC, in some embodiments. In otherembodiments, the cover layer 40 is formed by implanting impurities inthe Si core layer. The impurities can be boron, phosphorous and/orarsenic. The thickness of the cover layer 40 is in a range from about0.5 nm to about 10 nm in some embodiments, and is in a range from about1 nm to about 5 nm in other embodiments. The cover layer 40 can beformed by CVD, PVD, ALD, MBE and any other suitable film formationmethods. In certain embodiments, a cover layer 40 is not formed.

Next, as shown in FIG. 16, one or more metallic layers 120 and 130 areformed over the cover layer 40. If the cover layer 40 and/or the corelayer 30 is/are not formed, the metallic layers are formed over the corelayer 30 or the base membrane layer 20. In some embodiments, a firstmetallic layer 120 includes a layer of Mo, Zr, Nb and Ti, B or othersuitable material. In some embodiments, the second metallic layer 130includes a Ru layer. In some embodiments, a Ru layer 130 formed on a Molayer 120 is used. In other embodiments, a Ru layer 130 formed on a Zrlayer 120 is used. In certain embodiments, only a Zr layer is formed onthe cover layer 40. In certain embodiments, only a Ru layer is formed onthe cover layer 40. The thickness of the first metallic layer 120 isgreater than the thickness of the second metallic layer 130 in someembodiments. The thickness of each of the first metallic layer 120 andthe second metallic layer 130 is in a range from about 0.5 nm to about20 nm in some embodiments, and is in a range from about 1 nm to about 10nm in other embodiments. The second metallic layer 130 is thinner thanthe first metallic layer 120 in some embodiments. The first metalliclayer 120 and the second metallic layer 130 can respectively be formedby CVD, PVD, ALD, electroplating, and any other suitable film formationmethods.

Next, as shown in FIG. 17, a protection layer 50 is formed over themetallic layer 120, 130. The protection layer 50 includes one or morelayers of dielectric material, such as silicon oxide, silicon nitrideand silicon oxynitride. In certain embodiments, silicon oxide is used.In other embodiments, a stacked layer of silicon nitride formed onsilicon oxide is used. The thickness of the first protection layer 50 isin a range from about 500 nm to about 10 μm in some embodiments. Thefirst protection layer 50 can be formed by CVD, PVD, ALD, MBE and anyother suitable film formation methods. The first protection layer 50 canbe metal based material, for example, Al, Cu, Ta, Ti, Ni, Co, Fe, TaN orTiN and an alloy thereof. The first protection layer can be metal oxide,metal nitride such as SiN, SiO or SiON in some embodiments.

Next, as shown in FIG. 18, a hard mask layer 70 is formed over the backside of the substrate 10. The hard mask layer 70 includes one or morelayers of dielectric material, such as silicon oxide, silicon nitrideand silicon oxynitride. In certain embodiments, silicon nitride is used.The thickness of the hard mask layer 70 is in a range from about 100 nmto about 1000 nm in some embodiments, and is in a range from about 200nm to about 500 nm in other embodiments. The hard mask layer 70 can beformed by CVD, PVD, ALD, MBE and any other suitable film formationmethods.

Then, a photo resist layer 80 is formed on the hard mask layer 80, asshown in FIG. 19. The thickness of the photo resist layer 80 is in arange from about 1 μm to about 3 μm in some embodiments, One or morelithography operations are performed to pattern the photo resist layer80, and subsequently, the hard mask layer 70 is patterned by one or moreetching operations to form a first opening 90 as shown in FIG. 20. Thephoto resist layer 80 is removed by suitable resist removal operations.

Then, the substrate 10 is etched to form a second opening 95, as shownin FIG. 21. In some embodiments, wet etching using KOH, TMAH or EDP isperformed to etch the Si substrate 10. The substrate can also be etchedusing drying etching by one or more of SF₆, CF₄ and Cl₂ gas, mixed withN₂ and/or O₂ gas. In some embodiments, the substrate below the firstopening 90 is etched to expose the base membrane layer 20. By thisetching operation, a frame structure of the pellicle is formed by a partof the substrate 10 and a part of the hard mask layer 70.

Then, the protection layer 50 is removed by one or more etchingoperations, as shown in FIG. 22. In some embodiments, a wet etchingoperation is used. In some embodiments, a wet etching operation is used.In some embodiments, all of the layers of the pellicle are solid andnon-porous layers. In certain embodiments, all of the layers of thepellicle are inorganic.

FIGS. 23-28 show a sequential manufacturing operation for a pellicle foran EUV photo mask in accordance with an embodiment of the presentdisclosure. It is understood that additional operations can be providedbefore, during, and after processes shown by FIGS. 23-28, and some ofthe operations described below can be replaced or eliminated, foradditional embodiments of the method. The order of theoperations/processes may be interchangeable. Materials, configurations,dimensions, structures, conditions and operations the same as or similarto those explained with respect to FIGS. 1-22 may be employed in thefollowing embodiments, and some of the explanations may be omitted.Similarly, materials, configurations, dimensions, structures, conditionsand operations the same as or similar to those explained with respect toFIGS. 23-28 may be employed in the foregoing embodiments.

A substrate 10, for example a Si wafer, is prepared. The thickness ofthe substrate 10 is in a range from about 500 μm to about 1000 μm insome embodiments. On the substrate 10, a base membrane layer 20, as anetching stop layer, is formed, as shown in FIG. 23. The base membranelayer 20 functions as an etching stop layer in a subsequent substrateetching operation. The base membrane layer 20 includes one or morelayers of semiconductor material, such as SiC, SiGe, Ge, or dielectricmaterial, such as silicon oxide, silicon nitride and silicon oxynitride,or any other suitable material. In some embodiments, SiC is epitaxiallyformed on the substrate 10. In other embodiments, the base membranelayer 20 can be an amorphous or polycrystalline SiC, SiGe or Ge layer.In certain embodiments, the base membrane layer 20 is silicon nitride.The thickness of the base membrane layer is in a range from about 0.5 nmto about 40 nm in some embodiments, and is in a range from about 1 nm toabout 20 nm in other embodiments. The base membrane layer 20 can beformed by chemical vapor deposition (CVD), physical vapor deposition(PVD), atomic layer deposition (ALD), molecular beam epitaxy (MBE) andany other suitable film formation methods.

Next, as shown in FIG. 24, one or more metallic layers 120 and 130 areformed over the base membrane layer 20. In some embodiments, a firstmetallic layer 120 includes a layer of Mo, Zr, Nb, B, and Ti, Ru, orother suitable material. In some embodiments, the second metallic layer130 includes a Ru layer. In some embodiments, a Ru layer 130 formed on aMo layer 120 is used. In other embodiments, a Ru layer 130 formed on aZr layer 120 is used. In certain embodiments, only a Zr layer is formedon the cover layer 40. In certain embodiments, only a Ru layer is formedon the base membrane layer 20. The thickness of the first metallic layer120 is greater than the thickness of the second metallic layer 130 insome embodiments. The thickness of the first metallic layer 120 and thesecond metallic layer 130 is in a range from about 0.5 nm to about 20 nmin some embodiments, and is in a range from about 1 nm to about 10 nm inother embodiments. The second metallic layer 130 is thinner than thefirst metallic layer 120 in some embodiments. The first metallic layer120 and the second metallic layer 130 can respectively be formed by CVD,PVD, ALD, electro plating, and any other suitable film formationmethods. In some embodiments, all of the layers of the pellicle aresolid and non-porous layers. In certain embodiments, all of the layersof the pellicle are inorganic.

Next, as shown in FIG. 25, a protection layer 50 is formed over thesecond metallic layer 130. The protection layer 50 includes one or morelayers of dielectric material, such as silicon oxide, silicon nitrideand silicon oxynitride. In certain embodiments, silicon oxide is used.The thickness of the protection layer 50 is in a range from about 100 nmto about 10 μm in some embodiments. The protection layer 50 can beformed by CVD, PVD, ALD, MBE and any other suitable film formationmethods. The first protection layer 50 can be metal based material, forexample, Al, Cu, Ta, Ti, Co, Fe, Ni, TaN or TiN and their alloy. In someembodiments, multiple layers with different materials are used as thefirst protection layer 50.

Further, as shown in FIG. 25, a hard mask layer 70 is formed over theback side of the substrate 10. The hard mask layer 70 includes one ormore layers of dielectric material, such as silicon oxide, siliconnitride and silicon oxynitride. In certain embodiments, silicon nitrideis used. The thickness of the hard mask layer 70 is in a range fromabout 100 nm to about 1000 nm in some embodiments, and is in a rangefrom about 200 nm to about 500 nm in other embodiments. The hard masklayer 70 can be formed by CVD, PVD, ALD, MBE and any other suitable filmformation methods.

Then, a photo resist layer 80 is formed on the hard mask layer 80, asshown in FIG. 25. The thickness of the photo resist layer 80 is in arange from about 1 μm to about 3 μm in some embodiments, One or morelithography operations are performed to pattern the photo resist layer80, and subsequently, the hard mask layer 70 is patterned by one or moreetching operations to form a first opening 90 as shown in FIG. 26. Thephoto resist layer 80 is removed by suitable resist removal operations.

Then, the substrate 10 is etched to form a second opening 95, as shownin FIG. 27. In some embodiments, wet etching using KOH, TMAH or EDP isperformed to etch the Si substrate 10. In some embodiments, thesubstrate below the first opening 90 is etched to expose the basemembrane layer 20. By this etching operation, a frame structure of thepellicle is formed by a part of the substrate 10 and a part of the hardmask layer 70.

Then, the protection layer 50 is removed by one or more etchingoperations, as shown in FIG. 28. In some embodiments, a wet etchingoperation is used. In some embodiments, a wet etching operation is used.In some embodiments, all of the layers of the pellicle are solid andnon-porous layers. In certain embodiments, all of the layers of thepellicle are inorganic. As shown in FIG. 28, the core layer 30 and thecover layer 40 are not formed, and the first metallic layer 120 and thesecond metallic layer 130 are disposed directly on the base membranelayer 20. The pellicle is a three layer (only three layers) structure.

FIG. 29 shows a cross sectional views of pellicles for an EUV photo maskin accordance with another embodiment of the present disclosure. In thisembodiment, the frame structure has a tapered shape having a largeropening at the hard mask layer 70 side than at the base membrane 20side.

In some embodiments, a capping layer 25 is disposed between the basemembrane layer 20 and the core layer 30. The capping layer 25 includesone or more layers of dielectric material or metallic material. In someembodiments, one or more of silicon oxide, silicon nitride and siliconoxynitride, Ni, Al, Cu, Ta, Ti, TaN or TiN. The thickness of the cappinglayer 25 is in a range from about 0.5 nm to about 20 nm in someembodiments. The capping layer 25 can be formed by CVD, PVD, ALD, MBEand any other suitable film formation methods. In certain embodiments,no capping layer is formed on opposite side (substrate side) of the basemembrane layer.

EUV transmittance values and reflectance values at a wavelength of 13.5nm can be adjusted by selecting materials and/or thickness of thestacked structures of the pellicle. In some embodiments, the stackedstructure includes Ru/Mo/SiN/poly Si/SiN or Ru/Zr/SiN/poly Si/SiN. Inother embodiments, the stacked structure includes Ru/Mo/SiC orRu/Zr/SiC. For example, when a Zr layer is used instead of a Mo layer,it is possible to increase the EUV transmittance and to reduce EUVreflectance. Further, a SiC base membrane layer, which is less fragilethan polysilicon, also provides a higher EUV transmittance and a lowerEUV reflectance. By selecting the materials and/or thicknesses of thestacked layer of an EUV pellicle, it is possible to obtain an EUVtransmittance higher than about 85% in some embodiments, and higher thanabout 87% in other embodiments (and up to about 90%), and an EUVreflectance lower than 0.25% in some embodiments, and lower than 0.10%in other embodiments (or even smaller than 0.05% and as small as 0.01%).

FIG. 30 shows a cross sectional view illustrating a pellicle attached toan EUV photo mask in accordance with an embodiment of the presentdisclosure. The frame structure of the pellicle is attached to thesurface of the EUV photo mask with an appropriate bonding material. Thebonding material is an adhesive, such as acrylic or silicon based glueor A-B cross link type glue. The size of the frame structure is largerthan the area of black borders of the EUV photo mask so that thepellicle covers not only the circuit pattern area of the photo mask butalso the black borders.

FIG. 31 is a table showing EUV transmittance values and reflectancevalues at a wavelength of 13.5 nm for various stacked structures. Asunderstood form the table of FIG. 31, when a Zr layer is used instead ofa Mo layer, it is possible to increase the EUV transmittance and toreduce EUV reflectance. Further, a SiC base membrane layer, which isless fragile than polysilicon, also provides a higher EUV transmittanceand a lower EUV reflectance. By selecting the materials and/orthicknesses of the stacked layer of an EUV pellicle, it is possible toobtain an EUV transmittance higher than about 85% in some embodiments,and higher than about 87% in other embodiments (and up to about 90%),and an reflectance lower than 0.25% in some embodiments, and lower than0.10% in other embodiments (or even smaller than 0.05% and as small as0.01%).

In some embodiments of the present disclosure, a photo resist pattern isformed by using the EUV phot mask with the pellicle as described above.The EUV phot mask with the pellicle is set in an EUV exposure tool. Asubstrate (wafer) coated with a photo resist is also placed in the EUVexposure tool. An EUV light is generated at an EUV light source andguided on to the EUV phot mask through the pellicle. The EUV light isthen reflected by the EUV photo mask and the reflected light havingcircuit pattern information is guided on to the photo resist layer onthe substrate. The developing operation is performed to form a photoresist pattern. Then, by using the photo resist pattern as an etchingmask, an under-layer is pattered by one or more etching operations tomanufacturing patterns for a semiconductor device.

The pellicles according to embodiments of the present disclosure canprovide a higher strength and thermal conductivity (dissipation) as wellas higher EUV transmittance and lower EUV reflectance.

It will be understood that not all advantages have been necessarilydiscussed herein, no particular advantage is required for allembodiments or examples, and other embodiments or examples may offerdifferent advantages.

In accordance with an aspect of the present disclosure, a pellicle foran EUV photo mask has an EUV transmittance higher than 85% and an EUVreflectance lower than 0.25%, at a wavelength of 13.5 nm. In one or moreof the foregoing and following embodiments, the EUV transmittance ishigher than 87%. In one or more of the foregoing and followingembodiments, the EUV reflectance is lower than 0.10%.

In accordance with another aspect of the present disclosure, a pelliclefor an EUV photo mask includes a base membrane layer, a core layerdisposed over the base membrane layer, and one or more metallic layersdisposed over the core layer. In one or more of the foregoing andfollowing embodiments, the pellicle further includes a cover layerdisposed between the core layer and the one or more metallic layers. Inone or more of the foregoing and following embodiments, the cover layeris a silicon nitride layer. In one or more of the foregoing andfollowing embodiments, the cover layer is a doped region of a Si layer.In one or more of the foregoing and following embodiments, the basemembrane layer is made of SiC. In one or more of the foregoing andfollowing embodiments, the base membrane layer is made of siliconnitride. In one or more of the foregoing and following embodiments, theone or more metallic layers includes a first metallic layer and a secondmetallic layer disposed over the first metallic layer. In one or more ofthe foregoing and following embodiments, the second metallic layer is aRu layer. In one or more of the foregoing and following embodiments, thefirst metallic layer is a Mo layer. In one or more of the foregoing andfollowing embodiments, the first metallic layer is a Zr layer. In one ormore of the foregoing and following embodiments, the core layer is a Silayer. In one or more of the foregoing and following embodiments, the Silayer is a poly silicon layer.

In accordance with another aspect of the present disclosure, a pelliclefor an EUV photo mask includes a base membrane layer, and one or moremetallic layers directly disposed on the base membrane layer. In one ormore of the foregoing and following embodiments, the one or moremetallic layers includes a first metallic layer and a second metalliclayer disposed over the first metallic layer. In one or more of theforegoing and following embodiments, the second metallic layer is a Rulayer. In one or more of the foregoing and following embodiments, thefirst metallic layer is a Mo layer. In one or more of the foregoing andfollowing embodiments, the first metallic layer is a Zr layer.

In accordance with one aspect of the present disclosure, in a method ofmanufacturing a pellicle for an EUV photo mask, a base membrane layer isformed over a front surface of a substrate. A core layer is formed overthe base membrane layer. A cover layer is formed over the core layer. Afirst protection layer is formed over the cover layer. A secondprotection layer is formed over the first protection layer. A hard masklayer is formed on a back surface of the substrate. A first opening isformed in the hard mask by patterning the hard mask. The secondprotection layer is removed. A third protection layer is formed over thefirst protection layer. A second opening is formed in the substrate byetching the substrate through the first opening. The third protectionlayer and the first protection layer are removed. One or more metalliclayers are formed over the cover layer. In accordance with anotheraspect of the present disclosure, in a method of manufacturing apellicle for an EUV photo mask, a base membrane layer is formed over afront surface of a substrate, a core layer is formed over the basemembrane layer, a cover layer is formed over the core layer, one or moremetallic layers are formed over the cover layer, a first protectionlayer is formed over the one or more metallic layers, a secondprotection layer is formed over the first protection layer, a hard masklayer is formed on a back surface of the substrate, a first opening isformed in the hard mask by patterning the hard mask, the secondprotection layer is removed, a third protection layer is formed over thefirst protection layer, a second opening is formed in the substrate byetching the substrate through the first opening, the third protectionlayer and the first protection layer are removed. In one or more of theforegoing and following embodiments, the base membrane layer is made ofSiC. In one or more of the foregoing and following embodiments, the basemembrane layer is made of silicon nitride. In one or more of theforegoing and following embodiments, the core layer is a Si layer. Inone or more of the foregoing and following embodiments, the Si layer isa poly silicon layer. In one or more of the foregoing and followingembodiments, the cover layer is formed by implanting impurities in thecore layer. In one or more of the foregoing and following embodiments,the cover layer is a silicon nitride layer. In one or more of theforegoing and following embodiments, the one or more metallic layersincludes a first metallic layer and a second metallic layer disposedover the first metallic layer. In one or more of the foregoing andfollowing embodiments, the second metallic layer is a Ru layer. In oneor more of the foregoing and following embodiments, the first metalliclayer is a Mo layer. In one or more of the foregoing and followingembodiments, the first metallic layer is a Zr layer. In one or more ofthe foregoing and following embodiments, the first protection layer ismade of a dielectric material. In one or more of the foregoing andfollowing embodiments, the dielectric material includes silicon oxide orsilicon nitride. In one or more of the foregoing and followingembodiments, the second protection layer is made of a different materialthan the first protection layer and includes metallic material. In oneor more of the foregoing and following embodiments, the third protectionlayer includes a metallic material. In one or more of the foregoing andfollowing embodiments, the metallic material for the third protectionlayer is Ni. In one or more of the foregoing and following embodiments,the hard mask layer is made of dielectric material. In one or more ofthe foregoing and following embodiments, the dielectric material issilicon nitride.

In accordance with another aspect of the present disclosure, in a methodof manufacturing a pellicle for an EUV photo mask, a base membrane layeris formed over a front surface of a substrate. One or more metalliclayers are formed over the base membrane layer. A first protection layeris formed over the one or more metallic layers. A second protectionlayer is formed over the first protection layer. A hard mask layer isformed on a back surface of the substrate. A first opening is formed inthe hard mask by patterning the hard mask. The second protection layeris removed. A third protection layer is formed over the first protectionlayer. A second opening is formed in the substrate by etching thesubstrate through the first opening. The third protection layer and thefirst protection layer are removed.

The foregoing outlines features of several embodiments or examples sothat those skilled in the art may better understand the aspects of thepresent disclosure. Those skilled in the art should appreciate that theymay readily use the present disclosure as a basis for designing ormodifying other processes and structures for carrying out the samepurposes and/or achieving the same advantages of the embodiments orexamples introduced herein. Those skilled in the art should also realizethat such equivalent constructions do not depart from the spirit andscope of the present disclosure, and that they may make various changes,substitutions, and alterations herein without departing from the spiritand scope of the present disclosure.

The invention claimed is:
 1. A pellicle for an EUV photo maskcomprising: a frame portion made of Si; and a membrane disposed on theframe and including at least one metal layer, wherein: the membraneconsisting of equal to or less than five layers or equal to or more thanthree layers, the pellicle has an EUV transmittance higher than 85% andsmaller than 87.72% and an EUV reflectance lower than 0.25% and greaterthan 0.01%, at a wavelength of 13.5 nm, the membrane consists of: a basemembrane layer made of silicon nitride or SiC; a core layer disposed onthe base membrane layer; a cover layer disposed on the core layer andmade of a doped silicon layer; a first metal layer disposed on the coverlayer and made of Mo or Zr; and a second metal layer disposed on thefirst metal layer and made of Ru, a thickness of the core layer islargest in the membrane and in a range from 10 nm to 50 nm, a thicknessof the second metal layer is smaller than a thickness of the first metallayer, and a thickness of the cover layer is smaller than the thicknessof the first metal layer and in a range from 0.5 nm to 10 nm.
 2. Thepellicle of claim 1, wherein the EUV transmittance is smaller than86.88%.
 3. The pellicle of claim 1, wherein the EUV reflectance is lowerthan 0.20%.
 4. The pellicle of claim 1, wherein the base membrane ismade of SiC.
 5. The pellicle of claim 1, wherein the core layer is madeof poly silicon or amorphous silicon.
 6. The pellicle of claim 1,wherein, a thickness of the core layer is in a range from 20 nm to 40nm.
 7. A pellicle for an EUV photo mask, comprising: a frame portionhaving an opening; and a membrane disposed on the frame and consistingof five layers, wherein: the five layers are: a base membrane layer madeof silicon nitride or SiC; a core layer disposed on the base membranelayer and made of polysilicon or amorphous silicon; a cover layerdisposed on the core layer; a first metal layer disposed on the coverlayer; and a second metal layer disposed on the first metal layer, athickness of the base membrane layer is in a range from 1 nm to 40 nm,and a thickness of the first metal layer is in a range from 1 nm to 10nm and greater than a thickness of the second metal layer.
 8. Thepellicle of claim 7, wherein the frame portion is made of Si.
 9. Thepellicle of claim 7, wherein the cover layer is a silicon nitride layer.10. The pellicle of claim 7, wherein the cover layer is a doped regionof a Si layer.
 11. The pellicle of claim 7, wherein the second metallayer is a Ru layer.
 12. The pellicle of claim 7, wherein the firstmetal layer is a Mo layer.
 13. The pellicle of claim 7, wherein thefirst metal layer is a Zr layer.
 14. The pellicle of claim 13, whereinthe second metal layer is a Ru layer.
 15. The pellicle of claim 7,wherein the base membrane is made of SiC.
 16. The pellicle of claim 7,wherein the core layer is made of poly silicon.
 17. A pellicle for anEUV photo mask, comprising: a frame portion having an opening; and amembrane disposed on the frame and consisting of three layers, wherein:the three layers are: a base membrane layer made of SiC; a first metallayer disposed on the base membrane layer; and a second metal layerdisposed on the first metal layer, wherein a thickness of the secondmetal layer is smaller than a thickness of the first metal layer. 18.The pellicle of claim 17, wherein the second metal layer is a Ru layer.19. The pellicle of claim 18, wherein the first metal layer is a Molayer.
 20. The pellicle of claim 18, wherein the first metal layer is aZr layer.